This invention relates to interferometry and more particularly to real time interferometry for either comparing objects or for measuring small dimensional changes therein.
The gauging of manufactured parts by Moire techniques has generally been carried out by storing the master gauge on photographic film, which requires wet photographic processing as well as repositioning accuracy of the master, comparable to the finest measurement that is being made. A television technique for doing this is shown in U.S. Pat. No. 3,649,754 and eliminates these disadvantages, but introduces a sensitivity limit of its own, due to the limited resolution of the television camera. This is enlarged upon in an article describing the television techniques and the effect of the poor spatial resolution of the transducers which are used on system performance, which article is entitled "Time-lapse Interferometry and Contouring Using Television Systems." The article is published in APPLIED OPTICS, Vol. 10, No. 12, Dec. 1971, page 2722.